1. Field of the Invention
This invention relates to fluid handling processes and apparatus. More particularly, this invention relates to new methods and apparatus for enclosing fluidic oscillators or inserts so as to improve their performance.
2. Description of the Related Art
Fluidic inserts or oscillators are well known for their ability to provide a wide range of distinctive liquid sprays by cyclically deflecting, without the use of mechanical moving parts, the flow of a liquid jet. The distinctiveness of these sprays is due to the fact that they are characterized by being oscillatory in nature, as compared to the relatively steady state flows that are emitted from standard spray or shear nozzles.
U.S. Pat. No. 4,052,002 (Stouffer & Bray) shows in its FIGS. 5-7 some of the typical liquid droplet spray patterns that can be produced by fluidic oscillators (wherein the droplet patterns illustrated represent the droplets produced during one complete cycle of the cyclically deflected liquid jet). It shows what can be considered to be the essentially temporally varying, planar flow pattern of a liquid jet or spray that issues from the oscillator into a surrounding gaseous environment and breaks into droplets which are distributed transversely (i.e., in the assumed y-direction) to the jet's assumed, generally x-direction of flow. Such spray patterns may be described by the definable characteristics of their droplets (e.g., the volume flow rate of the spray, the spray's area of coverage, the spatial distribution of droplets in planes perpendicular to the direction of flow of the spray and at various distances in front of the oscillator's outlet, the average droplet velocities, the average size of the droplets, and the frequency at which the droplets impact on an obstacle in the path of the spray).
A fluidic insert is generally thought of as a thin, rectangular member that is molded or fabricated from plastic and has an especially-designed, liquid flow channel (or a means for inducing oscillations in the liquid that flows through the channel) fabricated into either its broader top or bottom surface, and sometimes both (assuming that this fluidic insert is of the standard type that is to be inserted into the cavity of a housing whose inner walls are configured to form a liquid-tight seal around the insert and form an outside wall for the insert's boundary surface/s which contain the especially designed flow channels). Pressurized liquid enters such an insert and is sprayed from it. Appropriate selection of the arrangement of the oscillator's flow channel and its dimensions are seen, at a specified flow rate, to control the properties of the sprayed oscillating liquid droplets.
Although it is more practical from a manufacturing standpoint to construct these inserts as thin rectangular members with flow channels in their top or bottom surfaces, it should be recognized that they can be constructed so that their liquid flow channels are placed practically anywhere (e.g., on a plane that passes though the member's center) within the member's body; in such instances the insert would have a clearly defined channel inlet and outlet. For example, see U.S. Pat. No. 5,820,034 (Hess) and its FIGS. 3-4 which show a two-part, fluidic insert whose exterior surface is cylindrical so that this insert can be fitted into a similarly shaped housing.
Additionally, it should be recognized that these flow channels need not be of a uniform depth. For example, see U.S. Pat. No. 4,463,904 (Bray), U.S. Pat. No. 4,645,126 (Bray) and RE38,013 (Stouffer) for fluidic oscillators in which the bottom surfaces of these channels are discretely and uniformly sloped so as to impact the ways in which the sprays from these oscillators spread as the move away from the oscillator's outlet.
There are many well known designs of fluidic circuits that are suitable for use with such fluidic inserts. Many of these have some common features, including: (a) at least one power nozzle configured to accelerate the movement of the liquid that flows under pressure through the insert, (b) an interaction chamber through which the liquid flows and in which the flow phenomena is initiated that will eventually lead to the spray from the insert being of an oscillating nature, (c) a liquid inlet, (d) a pathway that connects the inlet and the power nozzle/s, and (e) an outlet or exit from which the liquid exits the insert in the form of a spray.
Examples of fluidic circuits may be found in many patents, including U.S. Pat. No. 3,185,166 (Horton & Bowles), U.S. Pat. No. 3,563,462 (Bauer; feedback oscillator, which introduces some of the terminology that has become common in the fluidic oscillator industry, e.g., “power nozzle,” “feedback or control passage”), U.S. Pat. No. 4,052,002 (Stouffer & Bray), U.S. Pat. No. 4,151,955 (Stouffer; island oscillator), U.S. Pat. No. 4,157,161 (Bauer), U.S. Pat. No. 4,231,519 (Stouffer), which was reissued as RE 33,158, U.S. Pat. No. 4,508,267 (Stouffer), U.S. Pat. No. 5,035,361 (Stouffer), U.S. Pat. No. 5,213,269 (Srinath), U.S. Pat. No. 5,971,301 (Stouffer; box oscillator), U.S. Pat. No. 6,186,409 (Srinath), U.S. Pat. No. 6,253,782 (Raghu; mushroom oscillator), U.S. Pat. No. 7,014,131 (Berning et al.; double-sided oscillator), U.S. Patent Application Publication No. (USPAP) 2005/0087633 (Gopalan; three power nozzle, island oscillator), U.S. Pat. No. 7,267,290 (Gopalan & Russell; cold-performing mushroom oscillator), U.S. Pat. No. 7,472,848 (Gopalan & Russell; stepped, mushroom oscillator), U.S. Pat. No. 7,478,764 (Gopalan; thick spray oscillator), USPAP 2008/0011868 (Gopalan; interacting oscillators) and USPAP 2009/0236449 (Gopalan et al.; split throat oscillator).
Despite much prior art relating to the development of fluidic circuits, the nature of the housings or enclosures that surround fluidic oscillators have not changed much over the years. For example, for automotive windshield washing applications (one of the first areas in which such fluidic inserts were extensively used) a typical housing's exterior shape is aerodynamically configured from its rear face to its front face in consideration of the fact that this housing will be mounted on an automobile's hood and in front of its windshield. In such a housing's front face is an especially configured cavity or cavities that accommodate, via a press-fit insertion, one or two, see U.S. Pat. No. 6,062,491 (Hahn), fluidic oscillators. Such housings can also be modified to accommodate a diverging stack of such oscillators; see U.S. Pat. No. 7,111,800 (Berning et al.).
While one generally thinks of the enclosures for these oscillators as being of an almost totally enclosing nature, this need not be the case, see FIG. 3 from U.S. Pat. No. 5,845,845 (Merke et al.) which shows a “lid” for enclosing only the boundary surface of the oscillator in which the fluidic circuit is located.
As fluidic oscillators have continued to be used in more types of applications, the opportunity has arisen to re-examine and improve upon the design of their enclosures as a way to improve upon the overall spraying performance of the nozzle assemblies, etc. which use fluidic oscillators.